k8s-manifest-diff

k8s-manifest-diff

A CLI tool and Go library for parsing Kubernetes YAML/JSON manifests and computing diffs between sets of Kubernetes objects.

❯ dist/k8s-manifest-diff diff base.yaml head.yaml --output-format markdown
# Kubernetes Manifest Diff

## Summary
**Total Resources**: 4
**Changed**: 4 | **Created**: 0 | **Deleted**: 0 | **Unchanged**: 0

## Changed Resources (4)
- `Deployment/default/frontend-app`
- `Deployment/default/backend-app`
- `ConfigMap/default/app-config`
- `Secret/default/db-secret`

---

## Resource Changes

### apps/Deployment default/backend-app
```diff
--- backend-app-live.yaml
+++ backend-app.yaml
@@ -5,7 +5,7 @@
     annotations:
       app.kubernetes.io/managed-by: kubectl
       deployment.category: api
-      deployment.kubernetes.io/revision: "3"
+      deployment.kubernetes.io/revision: "2"
     labels:
       app: api
       environment: production
@@ -13,7 +13,7 @@
     name: backend-app
     namespace: default
   spec:
-    replicas: 4
+    replicas: 3
     selector:
       matchLabels:
         app: api
@@ -23,7 +23,7 @@
           app: api
       spec:
         containers:
-        - image: myapi:1.1
+        - image: myapi:1.0
           name: api
           ports:
           - containerPort: 8080

/Secret default/db-secret

--- db-secret-live.yaml
+++ db-secret.yaml
@@ -1,8 +1,8 @@
 object:
   apiVersion: v1
   data:
-    password: ++++++++++++++++
-    username: +++++++++++++++++
+    password: ++++++++++++++++++
+    username: +++++++++++++++++++
   kind: Secret
   metadata:
     annotations:

...

## Features

- CLI tool for comparing Kubernetes YAML manifests
- Flexible filtering options (exclude kinds, label/annotation selectors)
- Secret data masking for security (with option to disable)
- Summary mode for high-level diff overview
- Go library with simple API for programmatic usage
- Unified diff output with customizable context lines

## Installation

### Install CLI Tool

```bash
go install github.com/toyamagu-2021/k8s-manifest-diff/cmd/k8s-manifest-diff@latest

Install Go Library

go get github.com/toyamagu-2021/k8s-manifest-diff

CLI Usage

Basic Usage

Compare two Kubernetes YAML files:

k8s-manifest-diff diff base.yaml head.yaml

Filtering Options

Exclude specific resource kinds:

k8s-manifest-diff diff base.yaml head.yaml --exclude-kinds Job,CronJob,Pod

Filter by labels:

k8s-manifest-diff diff base.yaml head.yaml --label app=nginx --label tier=frontend

Filter by annotations:

k8s-manifest-diff diff base.yaml head.yaml --annotation app.kubernetes.io/managed-by=helm

Control diff context lines:

k8s-manifest-diff diff base.yaml head.yaml --context 5

Disable secret masking:

k8s-manifest-diff diff base.yaml head.yaml --disable-masking-secret

Show only summary of changes:

k8s-manifest-diff diff base.yaml head.yaml --summary

Version Information

k8s-manifest-diff version

Exit Codes

The tool follows standard Unix diff and ArgoCD conventions:

• 0: No differences found
• 1: Differences found
• 2: Error occurred (e.g., file not found, parsing error)

Library Usage

Simple YAML String Comparison

package main

import (
    "fmt"
    "github.com/toyamagu-2021/k8s-manifest-diff/pkg/diff"
)

func main() {
    baseYaml := `
apiVersion: v1
kind: ConfigMap
metadata:
  name: example
data:
  key: value1
`

    headYaml := `
apiVersion: v1
kind: ConfigMap
metadata:
  name: example
data:
  key: value2
`

    results, err := diff.YamlString(baseYaml, headYaml, nil)
    if err != nil {
        panic(err)
    }

    if results.HasChanges() {
        fmt.Printf("Changed resources: %v\n", results.FilterChanged().GetResourceKeys())
        fmt.Printf("Differences found:\n%s\n", results.StringDiff())
    } else {
        fmt.Println("No differences found")
    }
}

Custom Options

opts := &diff.Options{
    ExcludeKinds:           []string{"Job", "CronJob"},
    LabelSelector:          map[string]string{"app": "nginx"},
    AnnotationSelector:     map[string]string{"helm.sh/managed-by": "helm"},
    Context:                5,
    DisableMaskingSecret:   false, // Enable secret masking by default
}

results, err := diff.YamlString(baseYaml, headYaml, opts)
if err != nil {
    panic(err)
}

fmt.Printf("Changed resources: %v\n", results.FilterChanged().GetResourceKeys())
if results.HasChanges() {
    fmt.Printf("Diff:\n%s\n", results.StringDiff())
}

Build from Source

git clone https://github.com/toyamagu-2021/k8s-manifest-diff
cd k8s-manifest-diff
make build

Development

Prerequisites

• Go 1.25.0 or later
• Make

Build and Development Commands

# Build the project
make build

# Clean build artifacts
make clean

# Download and verify dependencies
make deps

# Tidy go modules
make tidy

# Format code and imports
make fmt

# Check formatting without modifying files
make fmt-check

# Run go vet
make vet

# Run all linting tools
make lint

# Run unit tests
make test

# Run E2E tests
make test-e2e

# Run all tests (unit + E2E)
make test-all

Package Architecture

The project is organized into the following packages:

• cmd/k8s-manifest-diff/: CLI application entry point with cobra-based commands
• pkg/parser/: YAML/JSON parsing using k8s.io/apimachinery
• pkg/diff/: Core diffing logic with filtering and secret masking
• testing/e2e/: End-to-end test scenarios

License

This project is licensed under the MIT License.

Contributing

Contributions are welcome! Please submit issues and pull requests on GitHub.